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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 221228A: Fermi GBM Final Real-time Localization
  2. GRB 221226B Swift-BAT refined analysis
  3. GRB 221226B: Swift-UVOT Detection
  4. GRB 221226A: AGILE detection
  5. GRB 221226B: Fermi GBM Observation
  6. GRB 221226B: Swift-XRT refined Analysis
  7. GRB 221226B: VLT/X-shooter redshift and host galaxy
  8. GRB 221226B: Enhanced Swift-XRT position
  9. GRB 221226B: Swift detection of a burst
  10. GRB 221226B: Fermi GBM Final Real-time Localization
  11. Swift GRB221226.95: Global MASTER-Net observations report
  12. Fermi GRB 221226A: Global MASTER-Net observations report
  13. GRB 221226A: Fermi GBM Final Real-time Localization
  14. Fermi-LAT gamma-ray observations of IceCube-221224A
  15. IceCube-221224A: BOOTES-4/MET Optical Upper Limit
  16. IceCube-221223A: BOOTES-4/MET Optical Observations
  17. Fermi-LAT gamma-ray observations of IceCube-221223A
  18. Fermi GRB 221223A: Global MASTER-Net observations report
  19. IceCube Alert 221224.04: Global MASTER-Net observations report
  20. IceCube-221224A - IceCube observation of a high-energy neutrino candidate track-like event
  21. GRB 221223A: Fermi GBM Final Real-time Localization
  22. IceCube Alert 221223.32: Global MASTER-Net observations report
  23. IceCube-221223A - IceCube observation of a high-energy neutrino candidate track-like event
  24. GRB 221221A: AGILE detection
  25. Fermi GRB 221221A: Global MASTER-Net observations report
  26. GRB 221221A: Fermi GBM Final Real-time Localization
  27. GRB 221218A: 3.6m DOT optical upper limit
  28. IceCube-221216A: No Candidate Counterparts from the Zwicky Transient Facility
  29. GRB 221216A: Detection by VZLUSAT-2
  30. GRB 221218A: MITSuME Akeno optical upper limits
  31. GRB 221218A: BOOTES-4/MET and OSN optical upper limits
  32. GRB 221218A: KAIT Optical Upper Limit
  33. IceCube-221210A: BOOTES-4/MET and Lijiang 2.4-meter Telescopes Optical Observations
  34. GRB 221215A: Fermi GBM Detection
  35. GRB 221218A: a long GRB detected by INTEGRAL
  36. Integral GRB221218.34: Global MASTER-Net observations report
  37. Fermi-LAT gamma-ray observations of IceCube-221216A
  38. IceCube-221216A: Upper limits from a search for additional neutrino events in IceCube
  39. GRB 221216A: Swift/UVOT Upper Limits
  40. GRB 221216A: Fermi GBM observation
  41. GRB 221216A: Swift-XRT refined Analysis
  42. Fermi-LAT gamma-ray observations of IceCube-221210A
  43. IceCube Alert 221216.25: Global MASTER-Net observations report
  44. GRB 221216A: AKO Upper Limit
  45. GRB 221215A: Swift-XRT observations
  46. GRB 221216A: Enhanced Swift-XRT position
  47. Swift GRB 221216A: Global MASTER-Net observations report
  48. GRB 221216A: Zadko observatory - Gingin optical observations
  49. GRB 221216A: Nanshan/NEXT optical upper limits
  50. GRB 221216A: Swift detection of a burst
  51. GRB 221216A: Fermi GBM Final Real-time Localization
  52. IceCube-221216A - IceCube observation of a high-energy neutrino candidate track-like event
  53. Fermi trigger No 692760884: Global MASTER-Net observations report
  54. GRB 221215A: Swift ToO observations
  55. GRB 221215A: Swift/BAT-GUANO arcminute localization
  56. Konus-Wind detection of GRB 221209A
  57. Fermi GRB 221215B: Global MASTER-Net observations report
  58. IPN triangulation of GRB 221209A (long)
  59. GRB 221215B: Fermi GBM Final Real-time Localization
  60. Fermi Gamma-ray Burst Monitor trigger 692760884/221215066 is not a GRB
  61. Swift GRB221215.15: Global MASTER-Net observations report
  62. Fermi trigger No 692713692: Global MASTER-Net observations report
  63. GRB 221215A: Fermi GBM Final Real-time Localization
  64. Swift Trigger 1144538 is not a GRB
  65. Fermi Gamma-ray Burst Monitor triggers 692721536/221214610 and 692713692/221214520 are not GRBs
  66. Konus-Wind detection of a burst from SGR 1935+2154 on 2022 December 13
  67. Fermi trigger No 692607435: Global MASTER-Net observations report
  68. GRB 221209A: CALET Gamma-Ray Burst Monitor detection
  69. IceCube-221210A: Upper limits from a search for additional neutrino events in IceCube
  70. GRB 221212A: Fermi GBM Final Real-time Localization
  71. Fermi GRB 221211A: Global MASTER-Net observations report
  72. GRB 221208A: AstroSat CZTI detection
  73. GRB 221211A: Fermi GBM Final Real-time Localization
  74. IceCube-221210A - IceCube observation of a high-energy neutrino candidate track-like event
  75. IceCube Alert 221210.36: Global MASTER-Net observations report
  76. GRB 221009A: MuSCAT3 observations
  77. GRB 221209A: AstroSat CZTI detection
  78. GRB 221210A: Fermi GBM Final Real-time Localization
  79. GRB 221209B: Fermi GBM Final Real-time Localization
  80. GRB 221209A: Fermi GBM observation
  81. GRB 221203C: AstroSat CZTI detection
  82. GRB 221209A: BALROG localization (Fermi Trigger 692257829 / GRB 221209243)
  83. GRB 221209A: Fermi GBM Final Real-time Localization
  84. GRB 221206B: Fermi GBM observation
  85. GRB 221206B: Swift-XRT observations
  86. GRB 221206B: Detection by GRBAlpha
  87. GRB 221206B: Swift/BAT-GUANO candidate arcminute localization
  88. GRB 221206B: Swift ToO observations
  89. Swift/BAT trigger #1143281 is not a GRB
  90. GRB 221206C: Fermi GBM Final Real-time Localization
  91. GRB 221206B: Fermi GBM Final Real-time Localization
  92. GRB 221206A: Fermi GBM Final Real-time Localization
  93. GRB 221205A: Fermi GBM Final Real-time Localization
  94. Swift GRB221204.45 AKO Upper Limit
  95. GRB 221202B: Detection by VZLUSAT-2
  96. Swift GRB221204.45: Global MASTER-Net observations report
  97. GRB 221203B: Fermi GBM Final Real-time Localization
  98. GRB 221202A: Swift/UVOT Detection
  99. GRB 221202A: Swift-BAT refined analysis
  100. GRB 221202A: VLT/FORS2 Afterglow Discovery

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Download all Circulars as a .tar.gz archive (updated once a day):
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